Teleconnection patterns and fisheries-environment interactions : case-studies from the Mediterranean

The impact of climate on fisheries resources has become a focal point for fisheries research. The objective of this thesis is to describe different aspects of the impact of teleconnections on marine ecosystems within the Mediterranean. Chapter I describes interactions between teleconnection patterns and oceanic variability in the Mediterranean. Atmospheric variability over the Atlantic and Eurasian sector forces oceanic circulation in the western Mediterranean, by altering the route of Atlantic storm tracks. The Indian monsoons are found to be related to gyre and upwelling formations in the eastern Mediterranean. Important links between the Mediterranean Oscillation and hemispheric circulation are also discussed. Chapter II studies the impact of atmospheric and oceanic forcing on the spatiotemporal distribution of chlorophyll-a concentration in the Mediterranean. A number of teleconnection indices with an important role in determining chlorophyll-a concentration are identified, especially for coastal areas, upwellings and gyres. Chapter III has an exploratory nature, with common trends in the landings of 41 fish species from the eastern Mediterranean identified and compared to fishing effort or large-scale environmental drivers. Teleconnections over the Atlantic or El Nino-related teleconnections, filtered by local SST and wind variability, are highlighted as driving forces behind some of the observed common landing trends. Chapter IV focuses on the biological complex of two commercial species, anchovy (Engraulis encrasicolus) and sardine (Sardina pilchardus). The results suggest that the West African Summer Monsoon, the East Atlantic Jet and the Pacific North American teleconnection patterns have a consistent correlation with anchovy and sardine distribution and abundance. Relationships between oceanic circulation in the Mediterranean and atmospheric variability over the neighbouring oceanic and continental masses were described and linked to biological variability. Oceanic structures that interrupt the oligotrophic regime of the area are affected by teleconnection patterns and in turn they influence fisheries productivity. Interactions between teleconnection patterns and fisheries can explain a large proportion of the observed fluctuations in marine resources and synchronicity between species and locations. The processes modulating the effects of climatic forcing vary at fine spatiotemporal scales, the different characteristics and habitat requirements of the species and interactions between the species. Further research is essential in order to delineate these effects and improve the management of marine resources in the persistently over-exploited environment of the Mediterranean Sea.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Environmental drivers of the anchovy/sardine complex in the Eastern Mediterranean

The anchovy/sardine complex is an important fishery resource in some of the largest upwelling systems in the world. Synchronous, but out of phase, fluctuations of the two species in distant parts of the oceans have prompted a number of studies dedicated to determining the phenomena, atmospheric and oceanic, responsible for the observed synchronicity and the biological mechanisms behind the population changes of the two species. Anchovy and sardine are of high commercial value for the fishing sector in Greece; this study investigates the impact of large-scale climatic indices on the anchovy/sardine complex in the Greek seas using fishery catches as a proxy for fish productivity. Time series of catches for both species were analysed for relationships with teleconnection indices and local environmental variability. The connection between the teleconnection indices and local weather/oceanic variation was also examined in an effort to describe physical mechanisms that link large-scale atmospheric patterns with anchovy and sardine. The West African Summer Monsoon, East Atlantic Jet and Pacific-North American (PNA) pattern exhibit coherent relationships with the catches of the two species. The first two aforementioned patterns are prominent atmospheric modes of variability during the summer months when sardine is spawning and anchovy juveniles are growing. PNA is related with El Nio Southern Oscillation events. Sea Surface Temperature (SST) appears as a significant link between atmospheric and biological variability either because higher temperatures seem to be favouring sardine growth or because lower temperatures, characteristic of productivity-enhancing oceanic features, exert a positive influence on both species. However at a local scale, other parameters such as wind and mesoscale circulation describe air-sea variability affecting the anchovy/sardine complex. These relationships are non-linear and in agreement with results of previous studies stressing the importance of optimal environmental windows. The results also show differences in the response of the two species to environmental forcing and possible interactions between the two species. The nature of these phenomena, e.g., if the species interactions are direct through competition or indirect through the food web, remains to be examined.</p

Environmental drivers of the anchovy/sardine complex in the Eastern Mediterranean

The anchovy/sardine complex is an important fishery resource in some of the largest upwelling systems in the world. Synchronous, but out of phase, fluctuations of the two species in distant parts of the oceans have prompted a number of studies dedicated to determining the phenomena, atmospheric and oceanic, responsible for the observed synchronicity and the biological mechanisms behind the population changes of the two species. Anchovy and sardine are of high commercial value for the fishing sector in Greece; this study investigates the impact of large-scale climatic indices on the anchovy/sardine complex in the Greek seas using fishery catches as a proxy for fish productivity. Time series of catches for both species were analysed for relationships with teleconnection indices and local environmental variability. The connection between the teleconnection indices and local weather/oceanic variation was also examined in an effort to describe physical mechanisms that link large-scale atmospheric patterns with anchovy and sardine. The West African Summer Monsoon, East Atlantic Jet and Pacific-North American (PNA) pattern exhibit coherent relationships with the catches of the two species. The first two aforementioned patterns are prominent atmospheric modes of variability during the summer months when sardine is spawning and anchovy juveniles are growing. PNA is related with El Nio Southern Oscillation events. Sea Surface Temperature (SST) appears as a significant link between atmospheric and biological variability either because higher temperatures seem to be favouring sardine growth or because lower temperatures, characteristic of productivity-enhancing oceanic features, exert a positive influence on both species. However at a local scale, other parameters such as wind and mesoscale circulation describe air-sea variability affecting the anchovy/sardine complex. These relationships are non-linear and in agreement with results of previous studies stressing the importance of optimal environmental windows. The results also show differences in the response of the two species to environmental forcing and possible interactions between the two species. The nature of these phenomena, e.g., if the species interactions are direct through competition or indirect through the food web, remains to be examined.</p

Atmospheric forcing on chlorophyll concentration in the Mediterranean

Recent research suggests the coupling of climatic fluctuations and changes in biological indices that describe species richness, abundance and spatiotemporal distribution. In this study, large-scale modes of atmospheric variability over the northern hemisphere are associated with chlorophyll-a concentration in the Mediterranean. Sea level atmospheric pressure, air temperature, wind speed and precipitation are used to account for climatic and local weather effects, whereas sea surface temperature, sea surface height and salinity are employed to describe oceanic variation. Canonical Correlation Analysis was applied to relate chlorophyll concentration to the above-mentioned environmental variables, while correlation maps were also built to distinguish between localized and distant effects. Spectral analysis was used to identify common temporal cycles between chlorophyll concentration and each environmental variable. These cycles could be interpreted as mechanistic links between chlorophyll and large-scale atmospheric variability. Known teleconnection patterns such as the East Atlantic/Western Russian pattern, the North Atlantic Oscillation, the Polar/Eurasian pattern, the East Pacific/North Pacific, the East Atlantic jet and the Mediterranean Oscillation are found to be the most important modes of atmospheric variability related to chlorophyll-a concentration and distribution. The areas that are mostly affected are near the coasts and areas of upwelling and gyre formation. The results also suggest that this influence may arise either through local effects of teleconnection patterns on oceanic features or large-scale changes superimposed onto the general circulation in the Mediterranean

Persistent gender bias in marine science and conservation calls for action to achieve equity

7 pages, 3 figures, 1 table, supplementary data https://doi.org/10.1016/j.biocon.2021.109134The increasing consideration of gender balance in conservation science and practice has been reflected in the setting of global commitments. Yet, women remain under-represented in science and conservation decision-making. We compiled and analyzed data on the representation of women in hiring, publishing, funding, and leadership positions in European Union marine sciences and conservation. To explore scientists' perceptions of gender imbalance in marine sciences and conservation more broadly, we conducted a global survey and analyzed 764 questionnaires from 42 countries. Participants were also asked to identify measures that promote gender equity. We found a consistent pattern of women being under-representated across institutions and nations characterized by a relatively balanced representation of men and women in early career stages and a growing gap in later stages, with women occupying only 13% to 24% of senior positions. The same pattern was found in publishing, funding, and leadership of research institutes. Survey results demonstrate that most marine scientists are aware of the general and persistent gender bias, and perceive that it may compromise our ability to effectively solve conservation problems. Measures that increase fairness in evaluations (e.g. for hiring) and that support work-life balance ranked high, whereas gender-oriented measures, such as gender-specific scholarships, received less support. Our findings suggest that mechanisms promoting a fairer share of family responsibilities and transparent processes in hiring and evaluation are the most promising path to a more balanced participation of women in scientific leadership and conservation decision-making. Such measures may benefit not only women but diversity more generallyThis article/publication is based upon work from COST Action 15121 “MarCons: Advancing marine conservation in the European and contiguous seas”, supported by COST (European Cooperation in Science and Technology; www.cost.eu).With the funding support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S), of the Spanish Research Agency (AEI)Peer reviewe

Portuguese purse seine fishery spatial and resource overlap with top predators

The Portuguese purse seine fishery, with average annual catches of 70 000 tonnes, operates mainly in coastal areas and targets small pelagic fish (SPF). Potential competition for resources may occur between the fishery and some species of marine mammals and seabirds, as suggested by observed incidental catches. For those species directly affected by the fishery, the spatial distribution of marine taxa and the fishing fleet are key pieces of information for spatial planning and management. We analysed the spatial and resource overlap between the fishery's distribution and effort, and the distribution and abundance of 6 species of top predators -seabirds (n = 4) and marine mammals (n = 2) between 2010 and 2014. Estimates of annual consumption by top predators and the fishery catch within the distributional range of one of their main prey species (sardine Sardina pilchardus) were also determined. Spatial overlap between all considered species and the fishery was low (0.7). Overall, values of consumption of SPF by the top predators were of the same order of magnitude as mean annual purse seine landings for the studied area. Our results can be used for marine spatial planning, including designation of Marine Protected Areas and the development of an ecosystem-based model for the effective management of the Portuguese purse seine fishery that takes into account the consumption of natural predators.project 'Life+ MarPro - Conservation of marine protected species in mainland Portugal' [NAT/PT/00038]info:eu-repo/semantics/publishedVersio

Effect of environmental drivers on the spatiotemporal distribution of mackerel at age in the Nordic Seas during 2010-2020

A joint spatio-temporal distribution model of mackerel (ages 3 to 10) was developed to investigate the age-based responses of mackerel to three environmental drivers: sea surface temperature (SST), mixed layer depth, and chlorophyll-a concentration during the summer months 2010-2020 in the Nordic Seas. The study showed that SST was the most important variable amongst the one tested and had the strongest impact on the distribution of the younger age classes (3-5) which had a narrower range of favourable SST and a stronger aversion to cold temperature than older individuals. Consequently, the impact of SST differed regionally; in the polar front regions, SST explained up to 61% of the variability in the observed density of young individuals where Arctic water masses likely acted as a barrier to these young individuals. That said, part of it could be confounded with the limited migration capability of young mackerels which could not reach the furthest frontal regions. In warmer southern waters, the same environmental variables had less explanatory power for mackerel of all ages. Individuals in the south were likely not constrained by temperature and perhaps more influenced by other variables such as food availability or ocean current (throughout their migration path), for which appropriate data are lacking. Moreover, the model showed that older mackerel were distributed more to the north and west and their migration pattern changed when the 2013 year-class no longer migrated to the west compared to previous year-classes. Additionally, all year classes started migrating more eastward from summer 2018